Conventional solar collectors have a low energy conversion efficiency. A typical flat panel photovoltaic (PV) panel converts only 15-20% of the incident radiant energy into electricity, while a typical flat panel thermal energy collector converts approximately 50% of the incident radiant energy into heat. Because they do not concentrate the solar energy, flat panel thermal collectors are typically incapable of being used in applications where it is desired to heat a fluid to temperatures above 150° F. This results in a “low quality heat” as it is referred to in the industry. A representative flat panel device is disclosed in U.S. Pat. No. 4,392,008 (hereinafter “Cullis”).
Conventional flat panel solar collectors are also expensive, primarily because they contain a large number of silicon solar cells. A typical PV panel producing approximately 250 W of electrical power contains approximately 20 square feet of silicon solar cells, which require solar grade silicon (e.g., 6N purity). Those cells are the most expensive component of the typical solar panel, even if the most inexpensive form of silicon suitable for solar panel use.
Because of their low efficiency and corresponding need for increased size, conventional solar collectors are typically large and heavy. This reduces their mounting options, or increases the expense and flexibility of mounting. This leaves the user limited in ability to use an optimum number of solar cells and limited in the ability to optimally locate the solar collector.
These disadvantages have led to a variety of attempted solutions involving concentrating the radiant solar energy. For example, Hines, et al. disclose concentrating “modules having a convenient size and market acceptance of traditional flat photovoltaic solar panels.” Pub. No. U.S. 2007/0193620 A1, which is incorporated herein by reference in its entirety. A lightweight, low-cost concentrating solar energy collector is disclosed by Hochberg and Costen (FIG. 1) that employs a parabolic reflector in a cylindrical housing. U.S. Pat. No. 6,994,082, which incorporated herein by reference in its entirety. Gilbert discloses a low concentrating photovoltaic thermal solar collector employing “at least one elongated cross-sectionally V-shape beam, a first and second sunray light reflecting surfaces integral to the respective interior faces of the V-shape beam side legs.” Pub. No. U.S. 2010/0282315, which is incorporated herein by reference in its entirety. But a disadvantage of such concentrating systems is that concentrated photovoltaic “operates most effectively in sunny weather since clouds and overcast conditions create diffuse light, which essentially cannot be concentrated.” U.S. Pub. No. U.S. 2010/0282315, which is incorporated herein by reference in its entirety.
By way of background, U.S. Pat. No. 6,111,190, which is incorporated herein by reference in its entirety, discloses a Fresnel lens solar concentrator made of light weight materials that can be used in space. U.S. Pat. No. 6,075,200, which is incorporated herein by reference in its entirety, discloses a stretched Fresnel lens solar concentrator for use in space. U.S. Pat. No. 6,031,179, which is incorporated herein by reference in its entirety, discloses a color-mixing lens for solar concentrator systems that increases power output by chromatically dispersing light. U.S. Pat. No. 5,505,789, which is incorporated herein by reference in its entirety, discloses a photovoltaic module using low-cost materials for high performance using an array of arched Fresnel lenses. U.S. Pat. No. 5,498,297, which is incorporated herein by reference in its entirety, discloses a photovoltaic receiver with a PV cell coupled to a heat sink using a Tefzel film. U.S. Pat. No. 4,719,904, which is incorporated herein by reference in its entirety, discloses a solar thermal receiver designed to minimize heat loss. U.S. Pat. No. 4,711,972, which is incorporated herein by reference in its entirety, discloses a PV cell for use with an optical concentrator. U.S. Pat. No. 4,672,949, which is incorporated herein by reference in its entirety, discloses another solar energy collector designed to minimize heat loss. U.S. Pat. No. 4,545,366, which is incorporated herein by reference in its entirety, discloses a bi-focused solar energy concentrator. U.S. Pat. No. 6,990,830, which is incorporated herein by reference in its entirety, discloses a system and method for supplying consumers with heat energy or cooling energy. U.S. Published Application No. 20010013207A1, which is incorporated herein by reference in its entirety, discloses a passive collimating tubular skylight for collecting radiant energy. WO2007109901A1, which is incorporated herein by reference in its entirety, discloses a support structure for a solar collector system. WO2007103300A1, which is incorporated herein by reference in its entirety, discloses a solar collector with a trough-like reflector and an absorber for receiving solar radiation. WO2007109899A1, which is incorporated herein by reference in its entirety, discloses an energy supply system using a thermal storage container and one or more solar collectors for use therewith. WO05090873A1, which is incorporated herein by reference in its entirety, discloses a solar collector with a linear reflector and an absorber spaced from the reflector for receiving solar radiation and conveying heat therefrom to a fluid. U.S. Pat. No. 4,224,082, which is incorporated herein by reference in its entirety, discloses a multi-functional solar collector pole. U.S. Pat. No. 4,323,052, which is incorporated herein by reference in its entirety, discloses a solar energy system. U.S. Pat. No. 4,392,008, which is incorporated herein by reference in its entirety, discloses a combined electrical and thermal solar collector. U.S. Pat. No. 4,491,681, which is incorporated herein by reference in its entirety, discloses a liquid cooled, linear focus solar cell for use with parabolic or Fresnel optical concentrators. U.S. Pat. No. 4,700,013, which is incorporated herein by reference in its entirety, discloses a hybrid PV and solar heat energy system and concentrator. U.S. Pat. No. 4,892,593, which is incorporated herein by reference in its entirety, discloses a solar energy collector using light funneling, a Fresnel lens, and a PV panel. European Published Application No. EP0384056A1 discloses solar collectors that generate both thermal and electric energy.
Thus, there presently exists the need for a solar energy collector with increased efficiency, a reduced need for silicon cells, a construction that increases mounting options by reducing weight and bulk, and improved performance in overcast conditions. Furthermore, solar panels are subject to failure, most commonly due to water damage to the panel. This causes added expense, loss of efficiency, and mounting limitations as traditionally it is recommended to not mount panels horizontally to avoid water collection. Water damage is also caused by commonly experienced environmental conditions, such as high humidity, rain, and condensation, making the use of solar cells in such environments challenging. There exists a need to reduce solar cell failure and provide an option that can minimize the challenge of using solar energy collectors in such environments.